It tends to overestimate HR-max in younger adults and underestimate in older ones. Tanaka (208 − 0.7 × age) is more accurate across all ages.

Is a low resting HR good?

Generally yes — endurance athletes often sit in the 40s–50s. Sudden changes in your resting HR can indicate over-training or illness.

What zone should I train in?

Most aerobic gains come from Z2 (60–70% HRR). Use Z4–Z5 sparingly — they require longer recovery.

Why are my zones higher than my watch says?

Different devices use different formulas. Pick one consistent method and stick to it for a season.

Can I rely on this if I have a heart condition?

No — talk to a cardiologist. They’ll prescribe personalised, safe HR targets.

Heart health · Training zones

Heart Rate Calculator

Target heart-rate zones for cardio training.

Your details

Age

years

Resting heart rateMeasure on waking, lying still

bpm

Max HR formulas are estimates with ±10 bpm individual variation. Tested values from a stress test are more accurate.

Estimated max HR

187bpm

Z1 — Recovery

Active recovery, warm-up, easy aerobic.

124–136 bpm

Z2 — Base / Endurance

Aerobic base — burn fat efficiently, build engine.

136–149 bpm

Z3 — Tempo

Moderate effort, sustained pace.

149–162 bpm

Z4 — Threshold

Hard intervals at lactate threshold.

162–174 bpm

Z5 — VO₂ max

All-out efforts, short intervals.

174–187 bpm

How max HR is estimated

We use the Tanaka equation, considered more accurate than the classic “220 − age”:

HR_max = 208 − 0.7 × age

Why we use the Karvonen formula

Instead of straight percentages of max HR, the Karvonen method anchors zones to your heart-rate reserve (max minus resting) — which is more individual and respects how fit you already are.

The five zones, in one minute

Z1 recovery · Z2 aerobic base · Z3 tempo · Z4 lactate threshold · Z5 VO₂ max. Most athletes spend 70–80% of training in Z1–Z2 and only short bursts in Z4–Z5.